In general, the processing of silver halide photographic light-sensitive materials, for example, the processing of a silver halide color photographic light-sensitive material, comprises fundamental processes of color development, desilvering and image stabilization including water washing. In the color development process, the color developing agent reacts with a silver salt to thereby imagewise produce a dye and developed silver. In the desilvering process, the developed silver produced in the color development process is oxidized (bleached) into a silver salt by a bleaching agent having oxidizing action and removed from the light-sensitive layer by a fixing agent which forms soluble silver together with unused silver halide, or the oxidation into a silver salt and the removal thereof are performed in one stage by a bleach-fixing solution. In the image stabilization process, the atmosphere of the image layer is adjusted to attain the stability of the image formed over a long period of time.
In the black-and-white development, the fundamental process also comprises development, desilvering and water washing.
In respective processing steps, an aqueous solution containing one or more processing chemicals (called a processing solution) is used. Each processing solution is relatively low in the concentration and accordingly, the system where a processing solution usable as it is, is produced by a manufacturer of processing chemicals, transported to a processing laboratory and stored, is generally inadequate in view of profitability, storage space or working.
In order to solve this problem, two methods have been conventionally used. One is a method of preparing a mixture of powder chemicals by mixing constituent components of the processing solution in a ratio according to the processing solution construction, packaging the mixture to form a so-called solid processing agent such as a solid powder preparation processing agent, supplying the solid processing agent to a processing laboratory, dissolving it in water at the processing laboratory to have an appropriate concentration, and using the dilution as the processing solution. Another is a method of dissolving the constituent components of the processing solution in a high concentration, filling the resulting concentrated solution into a container to produce a concentrated liquid processing agent, supplying the processing agent to a processing laboratory, diluting it with water to have a predetermined concentration at the laboratory, and using the dilution as a processing solution. The former solid processing agent is specifically described in U.S. Pat. Nos. 2,843,484 and 2,846,308, and Canadian Patent 831,928. With respect to the latter case, U.S. Pat. Nos. 3,574,619, 3,647,461 and 3,814,606, and British Unexamined Patent Publication No. 2,016,723 describe a concentrated liquid processing agent for color development and U.S. Pat. Nos. 3,467,521, 3,532,498, 3,894,948 and 4,046,571 describe a concentrated liquid processing agent for black-and-white development.
The solid processing agent is advantageous in view of the transportation cost and the storage space, however, it is inconvenient because of the work of dissolving at the processing laboratory and splashing of powder dust of chemicals as well as in respect of homogeneity of the composition prepared from the mixed chemicals and further disadvantageous in that the chemicals which are liquid at room temperature must be placed in a separate processing agent container and combined with the separately packaged powder agent.
On the other hand, the concentrated liquid processing agent is greatly advantageous in that the work of dissolving at the processing laboratory can be dispensed with, however, it is inferior to the solid processing agent in the convenience of transportation and storage. In this way, the solid processing agent and the liquid processing agent each has merits and demerits and the processing agents hitherto obtained have not yet succeeded in satisfying all aspects from the economical and environmental standpoint such as reduction in the processing agent volume, in the waste container, in the storage space and in the transportation cost, and from the simpleness and safety standpoint in working such as labor savings in the work of processing solution preparation.
In recent years, to cope with the requirements for improvement of the productivity in the photographic processing and for rapid processing, the concentration of the processing solution rather tends to have a higher concentration. When constituent components of a processing agent are contained at a concentration in excess of the solubility, insoluble components are separated and suspended in the solution and become bulky due to the grain growth by the coagulation mechanism or the Ostwald ripening mechanism. As a result, these matters sooner or later become incapable to be floating in the solution and start to precipitate. The precipitate is gradually solidified to lose flowability as the time elapses and turns into a bulky lump or adheres to the wall or bottom of the container, and then the processing solution is no more usable. Accordingly, the concentrated liquid processing agent must fundamentally be a homogeneous solution where the constituent components have a concentration less than the saturation solubility, so that it can be stable in the storage and free of any problem on use. Under these circumstances, reduction of volume by concentrating a solution is very hard to attain.
With respect to the improvement of the solid processing agent, a technique of forming a processing agent into a tablet is known (for example, in Canadian Patent 831928). However, a large amount of binder which is not necessary for the photographic processing is contained and therefore, there arises another problem that the load of dissolving work increases and floating residues are readily generated.
With respect to the liquid concentrated processing agent, pasting of a black-and-white development processing solution has been attempted for the various purposes such as concentrating and has been conventionally known, for example, in U.S. Pat. No. 2,735,774. The pasting has also been attempted for color developers. U.S. Pat. No. 2,784,086 discloses pasting using an alginic acid derivative as a tackifying agent, namely, a thickener. Japanese Published Unexamined International Application No. 57-500485 discloses a technique of pasting a concentrated liquid processing agent for color development. According to this technique, a processing agent is maintained in the concentrated paste state by adding silicon dioxide, sodium sulfate, lithium sulfate or diatomaceous earth which are photographically inactive. The addition of these aids is, however, accompanied by the increase of the ionic strength and not preferred for the concentrating. Further, the addition of these pasting aids causes useless reduction of the solubility and at the same time, lowers the activity coefficient of the processing solution constituent components.
Furthermore, the pasting is not to elevate the degree of concentration by increasing the solubility of constituent components but only delays the separation or if the separation starts, retards the cohesive solidification of insoluble matters to somewhat prolong the use term, and the volume reduction is not substantially solved. On the contrary, since the processing agent is reduced in the flowability, the workability at the processing laboratory is very impaired. In particular, the liquid processing agent loses its advantage such that the dissolving work can be dispensed with.
As described in the foregoing, the problems have not yet been solved at present in either approach from the side of solid processing agent or from the side of concentrated liquid processing agent.
The present inventor considered that if a concentrated liquid processing agent having both the small volume as an advantage of the solid processing agent and the flowability as an advantage of the liquid processing agent is obtained, the above-described problems can be solved and moreover, a liquid concentrated processing agent for silver halide photographic light-sensitive materials satisfying the requirements in various aspects such as profitability, environmental safety, workability and storage stability can be obtained, which is advantageous in that reduction in the volume of the processing agent, in the weight of the processing agent container, in the space for preservation and storage and in the cost for transportation of the processing agent can be realized, the powder chemicals as the constituent components can be rapidly and simply dissolved even in chilled water without any splashing or contact on the dissolving work for the preparation of a processing agent, and generation of tar due to air oxidation does not occur during the storage. The present inventor has found that such a composition can be realized by a concentrated processing agent composition in which the constituent components have such a high concentration that they cannot be completely dissolved and are present in the suspended state, nevertheless, the flowability having an apparatus kinematic viscosity of 25 cm.sup.2 /sec or less is maintained.
However, if a highly concentrated processing agent composition as above is produced by the usual method where the raw material chemicals are in sequence added to the mixing tank, colored floating matters are produced as the time passes and in addition, the insoluble suspended particles precipitate by coagulation, become bulky and solidify with the lapse of time and cannot be easily dissolved on use even by the dilution with water. Therefore, both the storage stability and the reproducibility in the production are not satisfied and a concentrated liquid composition capable of practical use cannot be obtained.